Ubuntu: How can I enable screenlock without turning off the monitor? (Ubuntu Gnome 14.04)

Question:

Ubuntu Gnome 14.04

When locking the screen, my monitor/screen turns off immediately.

I don't want that to happen immediately, more like after 30 minutes or so. Is that possible?

Solution:1

This is not possible anymore in Gnome 3. You would have to execute gsettings set org.gnome.settings-daemon.plugins.power idle-dim-time [seconds] (possibly as lightdm as this is the user who runs the lockscreen) however this key doesn't exist anymore.

A possible workaround Khurshid mentioned is to install XScreenSaver (and set the timeout from there):